Nanoscale Mapping of Magnetic Orientations with Complex X-ray Magnetic Linear Dichroism

TL;DR

This paper introduces a novel X-ray spectroptychography technique that significantly enhances the contrast and resolution of nanoscale magnetic domain imaging in compensated magnets by leveraging complex XMLD and phase contrast.

Contribution

It develops a coherent diffractive imaging method combining spectral XMLD mapping with hierarchical clustering to improve magnetic domain visualization.

Findings

Phase contrast outperforms absorption contrast in magnetic imaging.

The method achieves higher spatial resolution for magnetic domain mapping.

It provides element- and orbital-sensitive analysis of magnetic configurations.

Abstract

Compensated magnets are of increasing interest for both fundamental research and applications, with their net-zero magnetization leading to ultrafast dynamics and robust order. To understand and control this order, nanoscale mapping of local domain structures is necessary. One of the main routes to mapping antiferromagnetic order is X-ray magnetic linear dichroism (XMLD), which probes the local orientation of the N\'eel vector. However, XMLD imaging typically suffers from weak contrast and has mainly been limited to surface-sensitive techniques. Here, we harness coherent diffractive imaging to map the complex XMLD spectroscopically, and identify the phase linear dichroism as a high-contrast, high-resolution mechanism for imaging magnetic order. By applying X-ray spectroptychography to a model sample, we retrieve the full complex XMLD spectrum. Combining this with hierarchical clustering, we resolve the spatial distribution of probed domains by their distinct spectral signatures, providing a robust method for analyzing magnetic configurations with weak signals. Our results show that phase contrast is significantly stronger than the corresponding absorption contrast, offering higher spatial-resolution magnetic imaging. This approach establishes a reliable, element- and orbital-sensitive tool for studying compensated magnets.